[billybobsky]

So slime -- we all know they suck and tend to congregate in deep, lava-y places, but as a species of mob not often encountered several observations must be additionally made:

They do not appear to naturally despawn like other mobs, in fact, they don't.

They are visible at inordinate distances. I can see (with an x-ray texture pack) slimes 117+ blocks away actively jumping up and down, which is much greater than the reported 72 block radius active region around the player. Note: it is clear that Minecraft treats active chunks and viewable chunks differently -- viewing distance is quite significant on far, nearly 200 blocks which are loaded but not entirely active on the server. However, given the observation above, it is safe to assume that (like tamed wolves, seemingly) if you can SEE where the slimes are they count against the total number of hostile mobs, and thus, similar to tamed wolves which also do not despawn, can severely affect the number of hostile mobs spawning elsewhere. It seems in fixing the client side immortality of the slimes, Notch et al revealed a bug that probably had been lurking for slimes since their introduction. It isn't clear whether this will get fixed soon or ever ...

It is doubtful that this is the case, but it seems like slimes don't spawn NEAR cacti, in fact, I don't know how that aspect of the generic spawning algorithm is handled so it is possible that this is true for all mobs.

These behaviors in conjugate explain the intermittency of the mob spawns. In fact, I would suggest that the next time a lull in hostile mobs occurs someone don some x-ray goggles and go searching for their places of congregation and do whatever it takes to stop their spawning or encourage their death -- water and cactus, respectively. Lava does not kill them.

If you have any further observations about slimes feel free to share them here.